1. Field of the Invention
This invention relates to the field of ophthalmic optics and artificial lens adapted to be affixed to an eye and more specifically relates to an artificial lens adapted to be located in an eye having a macula and an enlarged pupil wherein the artificial lens comprises an optical lens system wherein each principal axis is eccentric to each other for directing light rays from each image of each lens onto the fovea centralis of the macula of an eye. In the preferred embodiment a first lens system having a prism directs paracentral light rays from a near object onto the fovea centralis of the macula and a second lens system having a prism positioned in a cooperating relationship to the first lens system directs central light rays from a distant object onto the fovea centralis of the macula of an eye.
This invention also relates to method for producing multiple images of an object for an eye having an enlarged pupil using an optical lens system wherein the principal axis of each lens system is eccentric to each other.
2. Description of the Prior Art
It is known in the art that when the optical power of the natural eye is emmetropic, the eye is naturally focused for distance with the ciliary body at rest. The natural eye has the ability to change (increase or decrease) the converging power of the natural (crystalline) lens for near vision and for intermediate vision, that is vision in the range of about 10xe2x80x3 to about 18xe2x80x3 or 20xe2x80x3.
With aging, the eye""s natural (crystalline) lens loses its ability to adequately increase its converging power. In order to provide for a sharp focus near vision, it is known in the art to make use of artificial lens systems. It is also known in the art to utilize a plurality of artificial lens systems such as spectacles (sometimes referred to as glasses), contact lens, intraocular lens, corneal lens and intracorneal lens, all of which are utilized to produce a focused near vision. Such lens systems are designed to use concentric lens systems for distant and near images and the images are passed through the natural round pupil as the only entrance of light to the retina.
Spectacles (sometimes referred to glasses) are well known in the art and are selected to have a diopter power to produce the correction required to focus near vision. Also, it is known in the art that such glasses or spectacles comprise bifocal lenses for near and distant vision correction or trifocal glasses for near, intermediate and distant correction vision, all of which use the central rays through the lens system chosen by the patient for use.
Contact lens likewise are well known in the art. Typical of the known prior art which describes contact lens are U.S. Pat. No. 3,034,403 relating to a contact lens of apparent variable light absorption characteristics; U.S. Pat. No. 3,270,099 which relates to a method for making multi-focal length, concentric contact lenses and U.S. Pat. No. 4,402,579 which discloses and teaches various concentric axes contact lenses structures.
Typically, contact lens are positioned over the anterior surface of the pupil. The natural crystalline lens and iris remain in place and perform their natural functions and cooperate with the contact lens to focus the appropriate images on the fovea centralis of the macula.
It is also known in the art to utilize prisms in glasses and spectacles both located along the same axis to improve the image focused on the natural crystalline lens.
U.S. Pat. No. 4,648,878 discloses a single lens in FIG. 6 thereof having a prism and wherein the lens is located in the posterior chamber.
It is also known in the art to utilize intraocular lens to replace the natural crystalline lens in a cataracts operation. Intraocular lens are implanted into either the anterior chamber or posterior chamber of the eye and are utilized in place of the natural crystalline lens. Typical of such intraocular lens are U.S. Pat. No. 4,010,496 which discloses a bifocal lens which is positioned within the anterior chamber; U.S. Pat. No. 4,244,060 which discloses an intraocular lens having a lens body and a plurality of lens-centering filaments extending outwardly in a common plane from spaced rim portions of the lens body; U.S. Pat. No. 4,485,499 which discloses intraocular posterior chamber lens and U.S. Pat. No. 4,976,732 which discloses an optical lens wherein the lens body has integral therewith a predetermined area which is adapted to selectively intercept and pass light through the lens body in a manner to obtain an optical effect for substitution of the loss of accommodation of a phakic, aphakic and pseudophakic eye.
U.S. Pat. No. 4,994,080 discloses an optical lens having stenopaeic openings located in the central area thereof which produces parallel light transmitting paths for passing light rays along a path defining the visual axis of the eye and forwarded onto the fovea centralis in a manner to obtain an optical effect by increasing the depth of focus of the eye in order to substitute for the loss of at least one of the focusing powers and the accommodation of the eye.
Artificial lens are also known in the art which are capable of being implanted onto the cornea anterior to the stromal surface of an eye. The artificial lens becomes encapsulated by growth of the corneal epithelium of the cornea of the eye over the anterior surface of the implanted lens implanting the same. One such artificial lens fabricated from a collagen-hydrogel material is disclosed in U.S. Pat. No. 5,112,350.
The natural (crystalline) lens degrades as the age of an individual approaches the 40-to-50-year-age range such that the natural lens can no longer adequately change shape due to an increase in rigidity and loss of elasticity of the lens of the eye causing defective accommodation and inability to focus sharply for near vision. This condition is referred to as a presbyopia.
When this occurs, an individual requires additional converging power (plus) for near vision. This is commonly supplied by the lower lens in a bifocal artificial lens, such as glasses. As the individual approaches the age of 65-70-years, substantially all of the natural converging powers of the lens is lost and additional convergence for near requirement must be made stronger. In such instances, the bifocal lenses of the glasses, contact lens or artificial lens must supply all of the convergence of light for near vision.
Following cataract extraction and intraocular lens implantation, there remains the need for additional convergence of light for near vision. With monofocal intraocular lens (xe2x80x9cIOLxe2x80x9d) focused for distance, the near vision convergence must be completely supplied by the bifocal glasses or a single vision reading glasses.
Multiple lens IOLs are known in the art and typically create multiple light rays or images which are directed on the macula. The artificial lens disclosed in U.S. Pat. Nos. 3,034,403 and 4,976,732 described above produce multiple light rays for the eye. Typically, the multiple lens IOLs do not have provisions for restricting the light from near and far and spontaneously flood the macula with excess light. Also, light passing through multiple lens IOLs enters the eye through each of the optical systems resulting in both a sharp image and a blurred image of the same image impinging upon the fovea centralis of the macula. This results in: (a) loss of color purity; (b) loss of contrast; and (c) inability of the retina to adapt since the brain perceives the flooding and receipt of extraneous light as too much light.
U.S. Pat. No. 4,906,245 discloses an implantable lens or contact lens adapted for use in an eye having a natural pupil as a replacement for a defective natural lens in the eye in which various portions of the lens have different powers and focal lengths to produce in-focus images on the retina of objects which are located at various distances from the eye, thereby substituting for the natural focusing action of the eye.
An intraocular lens that functions as a regular intraocular lens and, in tandem with or concentric with a high plus spectacle lens, as a Galilean telescope, was described in an article entitled xe2x80x9cThe Telescopic Intraocular Lensxe2x80x9d by Jeffrey Koziol, M. D., which appeared at pages 43 and 44 of a compilation of papers presented at the Eleventh National Science Writers Seminar in Ophthalmology, Sep. 16-Sep. 19, 1990, at Universal City, Calif. (the xe2x80x9cKoziol Referencexe2x80x9d). The Koziol Reference describes the telescopic intraocular lens as a teledioptic lens having a peripheral convex and central concave (minus) portion which have concentric axes. A full range of visual field and normal image size is achieved with the teledioptic lens. A magnified image is obtained when an image in a visual field is viewed through the minus portion of the lens and a high-plus spectacle.
None of the prior art discloses, teaches or suggests an artificial lens system adapted to be affixed to an eye having an enlarged natural pupil involving the separation of retinal images and directing light rays from both near and far images such that simultaneously different light rays of the same object strike the fovea centralis of the macula. In the preferred embodiment portions of the light rays are directed to locations superior and inferior to the fovea centralis of the macula.
The known glasses or spectacles having a prism do not place the prism on a selected surface of a lens to produce and direct disparate images to the fovea centralis of the macula.
The lens system disclosed in U.S. Pat. No. 4,648,878 does not disclose, suggest or teach an optical system having a first lens system and a second lens system for an eye having an enlarged natural pupil. The use of a prism in a single lens system does not result in the production of disparate images
The intraocular lens of the prior art utilized in the eye function to pass light rays of both near and far vision images onto the fovea centralis of the macula. Under certain light conditions, the macula is flooded with excess light thereby making it more difficult for the brain to interpret the image due to the presence of excess and not completely focused light.
In multiple lens IOLs, numerous light rays are presented to the macula through the multiple optical systems resulting in both a dull, less intense sharp image and a dulled, less intense blurred image of the same object. As a result, the retina is unable to adapt to the multiple images since the brain perceives the flooding of extraneous light and the blurred image as additional light making dark adaptation thereof difficult. The result is inadequate stimulation to drive the neurons. This is made worse when low illumination is present, such as at evening or at night.
The lens implant or contact lens system of U.S. Pat. No. 4,906,245 does not disclose, suggest or teach an optical system having a first lens system and a second lens system for implantation in an eye having an enlarged natural pupil.
The telescopic intraocular lens of the Koziol Reference requires use with a high plus, concentric spectacle to develop a magnified image.
The present invention relates to a novel, new and unique lens which is in the form of an artificial lens including a multifocal optical lens system having eccentric axes which is affixed to an eye. The lens of the present invention overcomes each of the above problems associated with the prior art while concurrently producing a system for developing specific light rays from near and distant images of objects which are focused on the fovea centralis of the macula.
The artificial lens of the present invention is adapted for use in an eye and comprises means adapted to be affixed to an eye having multifocal optical lens system wherein the principal axis of each lens is eccentric to each other for directing light rays from each image of each of the multifocal lens onto a fovea centralis of the macula of an eye. In the preferred embodiment, the artificial lens includes an image producing means comprising a first lens having a predetermined diopter power for receiving a near image and a prism having a preselected diopter power. The prism is positioned on a selected surface of the first lens and directs paracentral light rays from a near object onto the fovea centralis of the macula of the eye and central light rays of the near object superior of the fovea centralis of the macula. The artificial lens includes a second lens having a predetermined diopter power positioned eccentrically inferior of the first lens for receiving light rays from a distant object. The second lens may include a second prism having a preselected diopter power. The second prism is positioned on a selected surface of the second lens and directs paracentral light rays from the distant object onto a fovea centralis of the macula of the eye and central light rays from the distant object inferior of the fovea centralis of the macula. Also, a method is disclosed herein for producing multiple images for an eye comprising the step of affixing to an eye an artificial lens having a multifocal optical lens system wherein the principal axis of each lens is eccentric to each other for directing light rays from each image of each lens of the multifocal optical lens onto a fovea centralis of the macula of an eye.
There is no provision to selectively minimize or eliminate the light rays from one system while utilizing the other lens system. With the novel design of the present invention, the vertical eccentric arrangement of the lens systems makes it possible to selectively minimize the light rays from one of the lens systems by utilizing variations of eye lid positions in relation to the lens systems. For example, when concentrating on an object of regard, that is the specific objected desired to be viewed, from a distance through the distance lens system, the near lens system can be partially or completely occluded by the user intentionally lowering the upper lid. This results in xe2x80x9cpurificationxe2x80x9d (decrease in unfocused light) of the distance image. With the user adapts to use of the lens, the user""s positioning of the eyelid occurs without conscious attention. As the unused lens system is minimized by the lid, the brain perceives the change as xe2x80x9cbetterxe2x80x9d and it becomes natural to xe2x80x9cpurifyxe2x80x9d the image of the object of regard.
Although it is known in the prior art to utilize prisms in glasses, the prior art does not disclose, teach, suggest utilizing an artificial lens within the eye having a multifocal optical lens system wherein the principal axis of each lens system is eccentric to each other for directing light rays from each image of each lens of the multifocal optical lens system onto a fovea centralis of the macula of an eye. The artificial lens of the present invention maintains a separation of light rays from images of the two lens systems such that the fovea centralis of the macula will not be simultaneously presented with a fuzzy image and a clear image of the same object.
Thus, one advantage of the present invention is that the artificial lens system in the preferred embodiment is arranged such that the first lens system located superiorly in the eye having an enlarged pupil or artificial opening formed in the iris, when in use, permits light to pass therethrough onto the fovea centralis of the macula thereby directing paracentral light rays of a near object onto the fovea centralis of the macula and central light rays of the same object superior of the of the fovea centralis of the macula.
Another advantage of the present invention is that the multifocal optical system provides for near and distant correction of refractive error that does not use glasses or other similar external eye devices.
Another advantage of the present invention is that the two lens system in the lens optical system are eccentric and direct light rays from the same image onto the fovea centralis of the macula of an eye having an enlarged pupil wherein the principal axis of each optical lens system is eccentric to each other and the distance between each principal axis is selected to enable the first optical lens system and the second optical lens system to be operable within the enlarged pupil for directing light rays from a different object or the same object viewed through each of the first optical lens system and second optical lens system onto a fovea centralis of the macula of an eye.
The amount of separation of light rays of an image by a prism can be varied. If complete separation or disparity of the near and distance image is desired, a greater amount of prism can be placed in one or both of the first optical lens systems and second optical lens system to create this complete separation. If only slight disparity is desired, a very small amount of prism can be included in either or both of the distance and near lens systems. This very slight disparity has the effect of increasing depth perception or sterioposis. With the vertical eccentric arrangement, the image developed on the retina can be further purified by changing the relative lid positions in relation to the lens systems thereby eliminating certain rays which purifies the image of the object of regard. This is especially valuable in scotopic conditions such as with night driving. By eliminating the unfocused light, the retina and brain are able to dark adapt.
Another advantage of the present invention is that a prism may be used in one or both of the first optical lens systems and second optical lens system to control the amount of deflection of the paracentral light rays e.g., light rays which did not enter the eye through the center of the cornea. For example, when a single object is simultaneously observed by the user through the two optical lens systems, a small amount of prism may be used to either cause or maintain complete separation of the two images (complete disparity) or to cause the two images to be closely superimposed or substantially superimposed (leaving only slight disparity for the increase in depth perception or increase in sterioposis). Accordingly, in the preferred embodiment, a prism may be used to completely separate the image observed through the two optical lens systems or to control the amount of separation of the images to bring about superimposition or almost superimposition (slight disparity) to improve the quality of depth perception of the object of regard.
Another advantage of the present system is that the imaging producing means can be so arranged that when one lens system is in use, the light allowed to go through the other or unused lens system is minimized or completely eliminated. By placing the xe2x80x9cnear optical vision systemxe2x80x9d superiorly on the artificial lens, the upper eyelid position can be varied and thereby be utilized to cover up the nearest system while primarily using the xe2x80x9cdistant optical vision systemxe2x80x9d to pass selected paracentral light rays from an image onto the fovea centralis of the macula.
Another advantage of the present invention is that the natural pupil size can be altered or reconfigured by making the pupil larger and preferably an elongated vertically shaped elliptical natural pupil. By altering the pupil size or configuration, the quantity of available light is increased to 150% to 175% of the light that would have traversed the untreated or unaltered pupil. This is a marked improvement over the prior art lens system where the transmitted light is divided between the two lens system. Therefore, approximately 65% to 75% light (compared to the quantity of the light passing through the unaltered pupil before treatment) would be available for the lens system of the present invention to use to focus light rays from the images on the fovea centralis of the macula. If the pupil is not altered, only approximately 40% to approximately 45% of the light is available to be focused through each optical system.
This is typical of the numerous lens designs of the prior art as described above.
Another advantage of the present invention is that the artificial lens of the present invention can have one or both of the imaging lens systems configured with an extended objective lens anterior to the iris plane to function as a light gathering means.
Another advantage of the present invention is that the near lens system can be located in a superior position in an altered pupil, such as for example, in a natural pupil which is enlarged by forming the opening thereof into an oval shape resulting in a large geometrical dimension relative to the circumferencial edge of and, if desired, superior to the original edge of the pupil or an artificial opening formed superiorly in the iris.
Another advantage of the present invention is that further eccentricity of the near lens system is achievable by altering the natural pupil by vertical elongation of the natural pupil or by use of an accessory pupil. A prism may be used to optically cause greater image separation or a reduction in image separation by the eccentrically arranged lens system. This reduction can be complete, if desired, to increase the perception of depth, or almost complete, e.g. slight disparity. Thus, the accommodation of a single eye may be used to enhance depth perception which is different from and may be in addition to controlling or adjusting the depth perception or varying the amount of depth perception by varying the deflection angle, by use of a prism, between two eyes and/or the optical lens system used in both eyes.